BACKGROUND Bellis perennis L. (Asteraceae) (common daisy) is a herbaceous perennial plant known as a traditional wound herb; it has been used for the treatment of bruises, broken bones, and wounds. Bellis perennis has also been used in the treatment of headache, common cold, stomachache, eye diseases, eczema, skin boils, gastritis, diarrhea, bleeding, rheumatism, inflammation, and infections of the upper respiratory tract in traditional medicine. OBJECTIVE Antitumor activities of different fractions of B. perennis flowers at different concentrations were evaluated and through bioassay-guided fractionation and isolation procedures a saponin derivative (1) was isolated from the active fraction obtained from the n-butanol extract of flowers of the title plant by column chromatography. METHODS Antitumor activities of different fractions of B. perennis flowers at different concentrations were evaluated using Potato Disc Tumor Induction Bioassay. Structure elucidation of 1 was accomplished by spectroscopic methods [1D- and 2D-NMR, and LC-ESI(APCI)-TOF-MS(MSn)]. RESULTS The present study showed the antitumor activity of fractions obtained from B. perennis flowers for the first time. The most active fraction showed 99% tumor inhibition at 3000 mg/L. An oleanane-type saponin was isolated through bioassay-guided studies. CONCLUSIONS Through antitumoral bioassay-guided fractionation and isolation procedures, 1 was isolated from the active fraction of B. perennis. The detailed NMR data of compound 1 is given for the first time.